As semiconductor technology nodes advance, dimensions of interconnect metal lines in interconnect layers continue to shrink. As a result, in some conditions, an electrical current flowing through an interconnect metal line causes signal un-reliabilities and/or failures due to electromigration (EM) phenomena, which refer to changes in locations of atoms in the interconnect lines and layers. To improve the conditions, a precursor soak process with metal oxide, metal nitride and/or metal oxynitride and a plasma treatment are used in a formation of a capping layer over the interconnect metal lines. Such precursor soak and plasma treatment processes, however, cause damages to a low-K dielectric layer because of metal ion diffusion into the low-K dielectric layer, for example.
Like reference symbols in the various drawings indicate like elements.